Cross-country Skiers Research Articles

Eight Weeks of Bifidobacterium lactis BL-99 Supplementation Improves Lipid Metabolism and Sports Performance through Short-Chain Fatty Acids in Cross-Country Skiers: A Preliminary Study.

(1) Background: Probiotics in the form of nutritional supplements are safe and potentially useful for strategic application among endurance athletes. Bifidobacterium animalis lactis BL-99 (BL-99) was isolated from the intestines of healthy Chinese infants. We combined plasma-targeted metabolomics and fecal metagenomics to explore the effect of 8 weeks of BL-99 supplementation on cross-country skiers' metabolism and sports performance. (2) Methods: Sixteen national top-level male cross-country skiers were recruited and randomly divided into a placebo group (C) and a BL-99 group (E). The participants took the supplements four times/day (with each of three meals and at 21:00) consistently for 8 weeks. The experiment was conducted in a single-blind randomized fashion. The subject's dietary intake and total daily energy consumption were recorded. Blood and stool samples were collected before and after the 8-week intervention, and body composition, muscle strength, blood biochemical parameters, plasma-targeted metabolomic data, and fecal metagenomic data were then analyzed. (3) Results: The following changes occurred after 8 weeks of BL-99 supplementation: (a) There was no significant difference in the average total daily energy consumption and body composition between the C and E groups. (b) The VO2max and 60°/s and 180°/s knee joint extensor strength significantly increased in both the C and E groups. By the eighth week, the VO2max and 60 s knee-joint extensor strength were significantly higher in the E group than in the C group. (c) The triglyceride levels significantly decreased in both the C and E groups. In addition, the LDL-C levels significantly decreased in the E group. (d) The abundance of Bifidobacterium animalis increased two-fold in the C group and forty-fold in the E group. (e) Plasma-targeted metabolomic analysis showed that, after eight weeks of BL-99 supplementation, the increases in DHA, adrenic acid, linoleic acid, and acetic acid and decreases in glycocholic acid and glycodeoxycholic acid in the E group were significantly higher than those in the C group. (f) Spearman correlation analysis showed that there was a significant positive correlation between Bifidobacterium animalis' abundance and SCFAs, PUFAs, and bile acids. (g) There was a significant correlation between the most significantly regulated metabolites and indicators related to sports performance and lipid metabolism. (4) Conclusions: Eight weeks of BL-99 supplementation combined with training may help to improve lipid metabolism and sports performance by increasing the abundance of Bifidobacterium, which can promote the generation of short-chain fatty acids and unsaturated fatty acids, and inhibit the synthesis of bile acids.

The proportional distribution of training by elite endurance athletes at different intensities during different phases of the season.

The present review examines retrospective analyses of training intensity distribution (TID), i.e., the proportion of training at moderate (Zone 1, Z1), heavy (Z2) and severe (Z3) intensity by elite-to-world-class endurance athletes during different phases of the season. In addition, we discuss potential implications of our findings for research in this field, as well as for training by these athletes. Altogether, we included 175 TIDs, of which 120 quantified exercise intensity on the basis of heart rate and measured time-in-zone or employed variations of the session goal approach, with demarcation of zones of exercise intensity based on physiological parameters. Notably, 49% of the TIDs were single-case studies, predominantly concerning cross-country skiing and/or the biathlon. Eighty-nine TIDs were pyramidal (Z1 > Z2 > Z3), 65 polarized (Z1 > Z3 > Z2) and 8 "threshold" (Z2 > Z1 = Z3). However, these relative numbers varied between sports and the particular phases of the season. In 91% (n = 160) of the TIDs >60% of the endurance exercise was of low intensity. Regardless of the approach to quantification or phase of the season, cyclists and swimmers were found to perform a lower proportion of exercise in Z1 (<72%) and higher proportion in Z2 (>16%) than athletes involved in the triathlon, speed skating, rowing, running, cross-country skiing or biathlon (>80% in Z1 and <12% in Z2 in all these cases). For most of the athletes their proportion of heavy-to-severe exercise was higher during the period of competition than during the preparatory phase, although with considerable variability between sports. In conclusion, the existing literature in this area does not allow general conclusions to be drawn. The methods utilized for quantification vary widely and, moreover, contextual information concerning the mode of exercise, environmental conditions, and biomechanical aspects of the exercise is often lacking. Therefore, we recommend a more comprehensive approach in connection with future investigations on the TIDs of athletes involved in different endurance sports.

Olympic Games during nationwide lockdown: sports injuries and illnesses, including COVID-19, at the Beijing 2022 Winter Olympics

ObjectiveThe objective of this study is to describe the incidence of injuries and illnesses sustained during the Beijing Winter Olympic Games from 4 February 2022 to 20 February 2022.MethodsWe recorded...

Comprehensive analysis of performance, physiological, and perceptual responses during an entire sprint cross-country skiingcompetition.

To investigate performance, physiological, and perceptual responses of an entire sprint cross-country skiing competition in the skating style. Eighteen national-level male junior skiers participated in a simulated competition comprising an individual time trial (TT), followed by three heats (quarterfinals [QF], semifinals [SF], and final [F]). Participants' heart rate (HR) was continuously monitored while perceived readiness (RED, 1-10), rating of perceived exertion (RPE, 6-20), and blood lactate [La-] were assessed at standardized time points. The total duration and distance covered were 03:30 ± 00:06h and 25.2 ± 2.9km, respectively. The participants spent 02:19 ± 00:27h > 60% of their maximal HR (HRmax) and 00:16 ± 00:04h > 85% of HRmax. Average HR decreased from TT to F (89.3 ± 2.0% vs. 86.9 ± 3.0% of HRmax, P < 0.01). [La-] levels were highest before (4.6 ± 2.0 vs. 2.9 ± 1.2, 3.2 ± 2.0 and 2.5 ± 1.3mmol·L-1, all P < 0.01) and after (10.8 ± 1.4 vs. 9.8 ± 1.6, 9.1 ± 1.8 and 8.7 ± 1.7mmol·L-1, all P < 0.05) F compared to TT, QF, and SF, respectively. RED was lowest before F compared to TT, QF, and SF (6.6 ± 1.4 vs. 7.9 ± 1.1, 7.6 ± 1.1, and 7.4 ± 1.4, respectively, all P < 0.05) while RPE was highest after TT compared to QF, SF, and F (17.8 ± 0.9 vs. 15.1 ± 2.0, 16.5 ± 1.2 and 16.6 ± 1.8, respectively, all P < 0.01). The six best-performing skiers demonstrated higher RED before F (7.2 ± 0.9 vs. 5.3 ± 1.2, P < 0.05) and higher [La-] after F (11.2 ± 0.2 vs. 10.2 ± 0.3, mmol·L-1, P < 0.05) than lower-performing competitors. This study provides novel insights into physiological demands of an entire sprint cross-country skiing competition, which involves repeated 3-min high-intensity efforts interspersed with > 2h (25 km) of low- to moderate-intensity exercise.

The origins of the Canadian Birkebeiner Ski Festival: invented traditions, winter sportscapes, and heritage sport tourism in sustainability and the UNESCO Beaver Hills Biosphere

ABSTRACT The Canadian Birkebeiner Ski Festival emerged as the world’s third Birkebeiner cross-country ski loppet in 1985, emulating the Norwegian Birkebeiner and the American Birkebeiner. This study examines the early years of the Canadian Birkebeiner as a heritage sport tourism event with routes near Edmonton, Alberta, that became an annual festival and attraction in western Canada. Invented tradition, sportscapes, and heritage sport tourism are a conceptual frame to analyse how the Festival represented the Birkebeiner legends, how skiers and skiing constituted landscapes, and how the event contributed to sustainability. The Canadian Birkebeiner resulted in a winter sport festival and sportscape that shaped cross-country skiing, trails, and public lands, and was indicative of fluid social relations and rural place making by means of skiing. Based on archival and oral history sources, the study argues the Canadian Birkebeiner was an invented tradition that originated with a ski loppet instrumental in the negotiation of terrain for cross-country skiing that contributed to winter sportscapes and heritage sport tourism in the Cooking Lake-Blackfoot Provincial Recreation Area, and, ultimately, within the UNESCO Beaver Hills Biosphere. It contributes to studies of winter events with local and broader implications for sustainable heritage tourism.

Use of pharmaceuticals amongst athletes tested by Anti-Doping Norway in a five-year period.

The aim of the study was to map the use of pharmaceuticals by Norwegian athletes registered on doping control forms (DCFs) in a five-year period to examine general and some class specific use of pharmaceuticals across sports and athlete levels. Anonymous data from DCFs collected in 2015-2019 were manually entered into a database using the Anatomical Therapeutic Chemical (ATC) system for classification of the pharmaceuticals. Variables entered were year of control, gender, age group, athlete level, sport, test type, nationality, and pharmaceuticals (and dietary supplements) used. Pain killers in the ATC groups M01 A (Nonsteroidal anti-inflammatory drugs - NSAIDs) and N02 B (other analgesics), and anti-asthmatics in ATC groups R03 A and R03 B were the most frequently used pharmaceuticals. National level athletes reported more use of pharmaceuticals (1.4 ± 1.7 pharmaceuticals per form) than recreational level athletes (0.9 ± 1.2). The highest proportion of DCFs containing information about at least one pharmaceutical were found in speed skating (79.1%), alpine skiing (74.0%), rowing (72.4%) and cross-country skiing (71.7%). Painkillers were most frequently used in muscular endurance sports (30.4% and 21.2 % for M01A and N02 B, respectively) and ball and team sports (17.9% and 17.0%). Use of hypnotics was reported from ice-hockey players and alpine skiers in around 8% of the cases. Use of anti-asthmatics was most often reported amongst athletes specially exposed to cold, chemicals and heavy endurance training. Athletes in specialized sports requiring high levels of strength and/or endurance reported a higher use of pharmaceuticals out-of-competition compared to in-competition, while there was no such difference in complex sports, such as team, gymnastic, aiming and combat sports.

Characterisation of the Contact between Cross-Country Skis and Snow: On the Multi-Scale Interaction between Ski Geometry and Ski-Base Texture

In elite endurance sports, marginal differences in finishing times drive ongoing equipment improvement to enhance athlete performance. In cross-country skiing, researchers, since the 1930s, have faced the challenge of minimising the resistance caused by friction in the contact between skis and snow. This study was designed to evaluate the multi-scale interaction between the macro-scale ski-camber profile and the micro-scale ski-base texture. Considerations included real contact area, average interfacial separation, and total reciprocal interfacial separation between the ski and snow, which are properties that are intimately coupled to ski–snow friction. We found that both the profile of the ski camber and the texture of the ski base play decisive roles in determining viscous friction. At the same time, the texture of the ski base exerts a greater impact on the average real contact pressure, real contact area, and minimal average interfacial separation between the ski and snow than the ski-camber profile.

Effect of dihydroquercetin on oxidative metabolism in young athletes engaged in winter sports in a northern region

AIM: To study the effect of dihydroquercetin on the indicators of oxidative metabolism in young athletes engaged in the winter sports in the Khanty-Mansiysk Autonomous Okrug (KhMAO).&#x0D; MATERIAL AND METHODS: The indicators of oxidative metabolism were studied in a group of 56 male students (mean age 19.300.51 years) from the Khanty-Mansiysk boarding school of the Olympic reserve. These students were actively involved in winter sports such as cross-country skiing and biathlon. To assess the impact of the plant-derived antioxidant bioflavonoid Baikal dihydroquercetin (DHQ), the participants were administered a daily dose of 120 mg of DHQ for a period of 60 days. Measurements were taken before and after the exposure. Blood lipid peroxidation (LPO) products were studied, namely, lipid hydroperoxides (LHP) and products that react with 2-thiobarbituric acid products (PR-TBA). Additionally, we examined the indicators of the body's antioxidant defense system (ADS) through the assessment of total antioxidant activity (TAA) and thiol status (TS). To quantify the overall oxidative stress experienced by the participants, we calculated the oxidative stress coefficient (OSC) using the formula: OSC = LHP PR-TBA / TAA TS.&#x0D; RESULTS: The average levels of LPO values (HPL and PR-TBA) among KhMAO athletes have surpassed the upper limit of optimal values. On the other hand, the ADS parameters (TAA and TS) fall within the range of physiologically optimal values, albeit closer to the lower limit. Notably, athletes have exhibited an OSC increase that is nearly 3.5 times higher than the maximum allowable value. A quarter of the individuals examined displayed elevated HPL values, while more than 30% showed increased PR-TBA levels. A third of male athletes exhibited reduced ADS values compared to the physiologically optimal range. In total, 70.4% of skiers and biathletes in KhMAO have exceeded the OSC parameters. After two months of daily intake of 120 mg DHQ, the normalization of indicators of oxidative metabolism was observed. All parameters aligned with physiologically optimal values, except for OSC. We found a decrease in primary (LHP, 1.15 times) and secondary (PR-TBA, p=0.046) LPO indicators parallel to a significant increase in ADS indicators, specifically TAA (p=0.022) and TS (p=0.049). Conversely, there was a significant increase in ADS indicators, specifically TAA (p=0.022) and TS (p=0.049).&#x0D; Despite these positive changes, the OSC value, although significantly reduced (p 0.001) by 2.3 times compared to the initial value, remained above the upper limit of the physiological norm.&#x0D; CONCLUSION: The study demonstrated that young athletes engaged in winter sports experienced improved indicators of oxidative metabolism after a consistent two-month intake of the potent antioxidant DHQ. This led to the restoration of a balanced prooxidant-antioxidant state, enhanced overall well-being, and expedited recovery following intense physical exertion. Furthermore, our results may suggest that DHQ may contribute to prevention of non-communicable diseases in the future.

Effects of aerobic capacity on DNA telomere length in adolescent cross-country skiers

Effects of aerobic capacity on DNA telomere length in adolescent cross-country skiers

Investigation of the relationship between nutritional knowledge and nutritional supplement belief levels and athletic performances of elite cross-country skiers

The use of nutritional supplements provides support to the athlete, while the use of wrong and inappropriate supplements may adversely affect the performance of the athlete. This study investigated the relationship between the nutritional knowledge and nutritional supplement belief levels and athletic performances of elite cross-country skiers. A total of 19 elite cross-country skiers, 8 females and 11 males (mean age of 16.1±1.00 years) competing in the U-16 and U-18 categories, participated in the study. Inbody 120, 10 m, 20 m and 30 m sprint, agility, 20m shuttle run and hand grip tests were used to assess physical and psychological factors. Moreover, the Nutrition for Sports Knowledge Questionnaire (NSKQ) and the Sports Supplements Belief Scale (SSBS) were applied to the athletes. No significance was found in the comparison of the athletes in terms of Body Mass Index (BMI) classification (p&gt;0.05). A positive relationship was found between the NSKQ and age (r=0.466; p=0.044), body fat percentage (r=0.505; p=0.027), and body fat mass (r=0.642; p=0.003) values. On the other hand, a positive relationship was found between the SSBS scale and body weight (r=0.136; p=0.009), body muscle mass (r=0.681; p=0.001), total body water (r=0.647; p=0.003), hand grip strength (right hand r=0.621; p=0.005; left hand r=0.635; p=0.003), while a negative relationship was found between the SSBS scale and 10m sprint (r=-0.589; p=0.008), 20m sprint (r=-0.606; p=0.006), 30m sprint (r=-0.480; p=0.037) and agility values (r=-0.533; p=0.019). These findings demonstrate that the sports nutrition knowledge level does not have a positive effect on athletic performance, but it has a positive effect on body muscle mass, strength, sprint, and agility values that affect athletes’ athletic performances as athletes’ nutritional supplements belief levels increase.

Anthropometric features and functional state of the cardiovascular system in qualified athletes of various sports

Aim. To assess the anthropometric characteristics and functional state of the cardiovascular system in qualified athletes of various sports.Material and methods. A total of 136 male athletes were examined. Qualified athletes (n=116) (age, 22,07±4,10 years, sports experience 9,56±3,08 years) were divided into groups: I (n=30) — wrestling, judo, II (n=27) — cross-country skiing, biathlon, III (n=33) — powerlifting, IV (n=26) — volleyball. Control group (n=20) consisted of those training less than 3 years. We performed anthropometry with assessment of body height and weight, chest circumference, body surface area, body mass index (BMI), Pignet index, Erisman index, grip and back strength test. Echocardiography, cycle ergometry with assessment of physical working capacity (PWC170) and maximum oxygen consumption (MOC). The relationship between traits was assessed using the Spearman rank correlation coefficient (rs). Critical significance level was p=0,05.Results. According to echocardiography, qualified athletes had significant differences in structural parameters. Group II was characterized by an increase in left ventricular (LV) volumetric dimensions and identified correlations of BMI and body surface area with end-diastolic dimension (r=0,602), end-diastolic volume (r=0,591), end-systolic volume (ESV) (r=0,429), stroke volume (r=0,597), PWC170 (r=0,550). Groups I and III were characterized by an increase in LV posterior wall (LVPWT) and interventricular septal (IVST) thickness. In group I, there was a relationship between body surface area and LVPWT (r=0,413); Pignet index with MOC (r=0,623); PWC170 with Erisman index (r=0,573), strength of the right (r=0,610) and left hand (r=0,515), back muscles (r=0,445). Group III had the highest BMI and body surface area, while relationships were identified with LVPWT (r=0,426), IVST (r=0,409), LV mass (LVM) (r=0,453), and back muscle strength (r=0,464); the Erisman index correlated with LVM index (r=0,359). In group IV, the parameters of height, body weight and body surface area are interrelated with LVM (r=0,731), LVPWT (r=0,523), IVST (r=0,399), ESV (r=0,504), end-systolic dimension (r=0,467), right hand strength (r=0,583).Conclusion. The relationships established by correlation analysis showed that anthropometric features are important components and criteria for assessing cardiac hemodynamics function in qualified athletes, depending on the type of sport and the duration of training, which must be taken into account when achieving sports results.

P08.09.B EFFECTS OF A ONE-WEEK SKIING INTERVENTION ON LOWER LIMB MUSCLE STRENGTH IN BRAIN TUMOR PATIENTS AND THEIR CAREGIVERS

Abstract BACKGROUND Due to fatigue or feelings of insecurity, many brain tumor patients are not sufficiently active. Among other things, this puts patients at higher risk for sarcopenia predicting overall survival. Exercise interventions of various kinds could effectively counteract this problem. Here, we aim to present the impact of a one-week skiing intervention on leg muscle strength in brain tumor patients and their caregivers as well as feasibility and safety of the intervention. MATERIAL AND METHODS Ten brain tumor patients and their families participated in this one-week skiing intervention in a self-catering lodge at 1400m altitude. Daily 4-hour ski sessions (including approx. 1 hour rest) with professional ski instructors were performed in small groups (≤5 participants) divided by proficiency level. Participants could choose between downhill and cross-country skiing. Adverse events were noted daily. Muscle strength was determined 3-10 days pre- and postintervention on 5 different gym machines (knee extension, knee flexion, adductors, abductors, leg press) using Brzycki's equation. RESULTS 20 adults (10 patients, 10 caregivers) and 7 children participated in the ski-based intervention. All patients were surgically treated at least once and received chemo- and/or radiotherapy (ongoing chemotherapy in 6 patients). No severe adverse events were recorded throughout the week. 15 adults (9 patients, 56% female; 6 caregivers, 67% female) aged 21-69 years (mean 50 years) completed the muscle strength tests. Of those, most patients suffered from grade 4 brain tumors (67%), followed by grade 2 (22%) and grade 1 (11 %) tumors. Mean muscle strength increased in all muscle groups tested (knee extension +13.5%, p=.024, CI 95%: -0.5 - 29.1; knee flexion +7.1%, p=.048 CI 95%: -1.0 - 14.0; adductors +6.6%, p=.039, CI 95%: 1.3 - 13.4; abductors 20.0%, p=.004, CI 95%: 6.9 - 35.7; leg press +19.5%, p=.050, CI 95%: -5.6 - 44.6). Tumor grade, gender, type of ski intervention, and age did not affect the RESULTS . CONCLUSION During one week of intensive ski training, positive effects on leg muscle strength could be shown in both brain tumor patients and their families regardless of age, gender, downhill/cross-country ski, or WHO grading. Furthermore, this study demonstrates feasibility and safety of ski-based exercises in this patient population. Interventions such as these could help patients overcome (gait) insecurities and motivate them to become more physically active in their daily lives. In the longer term, this may lead to better management of everyday life and improved quality of life.

Effects of adding high-intensity training during an 8-week period on maximal oxygen uptake in 12-year-old youth athletes.

Maximal oxygen uptake (V̇O2max ) increases during adolescence parallel to the increase in fat-free mass (FFM). How much endurance training adds to this effect is still controversial. Our aim was to investigate if inclusion of high-intensity training (HIT) during an 8-week training period was superior to low-intensity strength and coordination training in 12-year-old youth athletes concerning the effect on V̇O2max . Thirty-five cross-country skiers were randomized into a HIT group (ET) and a strength and coordination group (SC), while 29 less active peers served as controls for growth and maturation (C). Anthropometrics and V̇O2max were assessed before and after the training period, and level of physical activity and training were monitored with accelerometers, training logs and a questionnaire. The number of weekly training sessions were higher for ET (4.6 ± 1.2) and SC (4.1 ± 1.0) compared with C (1.8 ± 2.0) (p < 0.01), with only ET conducting HIT sessions (1.9 ± 0.2 per week). C spent more time sedentary and less time in moderate and vigorous activity compared with ET (p < 0.05). All groups had a similar %-change pre-post in absolute V̇O2max (mL min-1 ) of 6% ± 6% for ET (p < 0.01), 5% ± 7 for SC (p = 0.14), and 5% ± 13% for C (p = 0.03), with no significant differences between groups. V̇O2max relative to FFM did not change significantly for any groups. The change in V̇O2max paralleled the change in FFM for all groups, questioning the effect of HIT on V̇O2max over an 8-week period in youth athletes.

Non-exercise-based racing time prediction of cross-country skiers using machine learning methods combined with Relief-F feature selection

This study proposes new non-exercise models for estimating the racing time of cross-country skiers. Machine learning methods employed to build the prediction models include General Regression Neural Network (GRNN), Support Vector Machine (SVM), Multilayer Feed-Forward Artificial Neural Network (MFANN), and Radial Basis Function Neural Network (RBFNN), whereas the Relief-F algorithm combined with a ranker search has been utilized as the feature selector. The self-created data set contains samples collected from 370 cross-country skiers with inhomogeneous capabilities. Each sample in the data set contains physiological variables such as sex, age, height, weight, and body mass index (BMI) combined with an immersive set of survey data. The outcomes suggest that generally, the GRNN-based models exhibit the best prediction performance and can be used as a feasible tool for the prediction of the racing time of cross-country skiers with tolerable root mean square errors (RMSEs). It is seen that inclusion of age and assigned starting wave of cross-country skiers in models leads to much lower RMSEs, suggesting that the racing time of cross-country skiers is highly correlated to these two predictor variables. When compared with the exercise-based models, the proposed non-exercise-based models produce consistently comparable prediction performance for all evaluated machine learning methods. The non-exercise-based models have the relevant benefit of practical feasibility, as the models do not require the skiers to complete physical exercises and are also applicable to a wide range of cross-country skiers.

Rest Energy Expenditure and Energy Expenditure During Submaximal Exercise: New Approach to Assessment of Performance in Skiers

The aim of the present study was to analyse rest energy expenditure (REE) and energy expenditure (EE) during submaximal exercise according to performance of athletes. A retrospective analysis of data from 2014 to 2020 among cross-country skiers in the preparatory phase was performed. Depending on the potential performance athletes (n = 136) were divided into two groups: I – test completed to the anaerobic threshold (AnT), II – test completed until exhaustion. The present study included the data only before AnT for a correct comparison of the results. REE was 2058.5 ± 220.5 kcal/day in I group and 2023.1 ± 216.4 kcal/day in II group (p = 0.481). In REE structure, the contribution of fats and carbohydrates (CHOs) was 69 and 31% in I group, 48 (p = 0.021) and 52% (p 0.000) in II group. Correlations between VO2rest and REE, as well as the rate of fats and CHOs oxidation at rest were revealed. In I and II groups the VO2AnT (p 0.000) and relative values of VO2max (p 0.05) were significantly different. EE before AnT was 135.9 ± 31.2 and 134.0 ± 23.4 kcal (p = 0.399) for I and II groups. The present study showed that the balance 1 : 1 of fats and CHOs in the REE structure is a more informative performance marker than quantitative assessment of EE. VO2AnT reduced by 20% relative to VO2max may indicate the functional economization and the body’s ability to perform exercise during long time, including in the anaerobic exercise. Endurance athletes demonstrated economy of CHOs against actively using of fats during submaximal exercise. Complex estimated of performance indicators and EE (including contribution fats and CHOs) should be taken into account when studying the performance of athletes.

Electric Field of the Heart on the Thorax Surface in Highly Trained Athletes during Initial Ventricular Activity

The article is focused on the study of the electrical remodeling of the “sports heart” using multichannel ECG mapping to make a more detailed and informative analysis of the excitation of the myocardium remodeled by sport activity. The study of the heart electrical activity was carried out from 64 unipolar electrodes on the thorax surface synchronously with standard limb leads in highly trained cross-country skiers (n = 15) and young non-trained men (n = 19) at rest. The amplitude-temporal and spatiotemporal characteristics of the electric field of the heart were measured. By the typical distribution of areas of the negative and positive cardiac potentials the durations of depolarization and its individual phases were estimated. ECGII was used to determine the duration of the R-R, PQ (PR), QRS, QT, QTc intervals; in the unipolar lead V5 the R-wave peak time (RWPTV5) was measured. In athletes, the duration of PQII, QTII, QTcII, RWPTV5 intervals were statistically significantly longer than in non-trained men. Analysis of the electrical field of the heart showed a difference in the ratio of the phases of ventricular depolarization in athletes and non-trained individuals at rest. The onset of ventricular depolarization and the first inversion of cardiac potential in athletes were significantly earlier than in non-trained people, while the completion and total duration of the period of ventricular depolarization did not differ. In skiers, the duration of the first inversion was significantly longer than in non-trained individuals; a tendency to shortening of the second period of stable location of potentials on the thorax surface was also shown. The use of surface ECG mapping made it possible to reveal differences in the spatiotemporal organization of heart ventricular depolarization between cross-country skiers and non-trained men at rest. The results of the study may be useful in the analysis of the electrical remodeling of the heart in athletes training the physical quality of endurance.

Dynamics of TP, HF-, LF- and VLF- Waves of the Cardiointervalogram (in Clinostasis Conditions) of an Elite Ski Racer in the Preparatory, Competitive and Transitional Periods, Depending on the Volume and Intensity of Training Loads

In order to study the mechanisms of adaptation to loads requiring high endurance, the 27-year-old master of Sports of Russia in cross-country skiing repeatedly recorded a cardiointervalogram (CIG) under clinostasis conditions, estimating TP, absolute power (mc2) of LF-, HF- and VLF-waves and the relative (as a percentage of TP) power of these waves, i.e. LF%, HF% and VLF%. They were compared with the volume (Vkm, Vmin) and intensity (Nhr) of training loads. The volume of loads was maximum in the preparatory period (21 km/day) and it is minimal in the transition period (18 km/day), and their intensity throughout the annual cycle was stable (working pulse – 120–121 beats/min). With the change in the volume of loads, the values of the KIG indicators also changed. So, in the preparatory period, the medians of TP, the power of HF-, LF- and VLF-waves, as well as VLF% increase; in this period, with an increase in the volume of loads (Vkm), the values of VLF% increase. In the competitive period, the medians of TP, the power of HF-, LF- and VLF-waves and VLF% remain at a high level. In the transition period, the median of TP, the power HF-, LF- and VLF-waves, as well as LF% and VLF%, but the median of HF% increases. For the annual cycle, a direct dependence of the median of TP on the volume of loads (Vkm) and the median power of VLF waves on the volume (Vkm) and intensity (Nhr) of the load was revealed. It is postulated that the values of TP, HF-, LF-, and VLF-waves, as well as VLF% (in clinostasis) reflect the influence of the Cholinergic system on the heart, while VLF% probably reflects the intensity of synthesis of non-neuronal heart’s acetylcholine, and the values of LF% and HF% reflect the formation of anxiety in connection with upcoming starts.

Elite skiers'experiences of heat- and moisture-exchanging devices and training and competition in the cold: A qualitative survey.

Winter endurance athletes have a high prevalence of exercise-induced bronchoconstriction (EIB) and asthma, probably due to repeated and prolonged inhalation of cold and dry air. Heat- and moisture-exchanging devices (HME) warm and humidify inhaled air and prevent EIB. The aimof this study was to share cross-country skiers and biathletes'experiences of training and competition in low temperatures, views on temperature limits, usage of HME, and consequences of cold exposure on their health. Eleven Swedish World Championship or Olympic medalists in cross-country skiing and biathlon were interviewed and transcripts were analyzed using qualitative content analysis. Participants described how cold temperatures predominantly affected the airways, face, and extremities. During training, extreme cold was managed by choosing warmer clothing, modification of planned sessions, use of HME, delaying training, or changing location. In competition, participants described limited possibility for such choices and would prefer adjustment of existing rules (i.e., more conservative temperature limits), especially since they understood elite skiing in low temperatures to present an occupational hazard to their health. Participants had at times used HMEs during training in cold environments but described mixed motives for their use-that HMEs warm and humidify cold inhaled air but introduce additional resistance to breathing and can cause problems due to mucus and ice build-up. Skiers also perceived that they had become more sensitive to cold during the latter part of their careers. The present study gives a unique insight into the "cold" reality of being an elite athlete in skiing and biathlon. Cold exposure results in negative health consequences that are preventable, which means that rules must be followed, and organizers should acknowledge responsibility in protecting athletes from occupational hazards. Development of evidence-based guidelines for protection of athletes'respiratory health should be a focus for future translational research.

Test-retest reliability of ski-specific aerobic, sprint, and neuromuscular performance tests in highly trained cross-country skiers.

Laboratory tests are commonly performed by cross-country (XC) skiers due to the challenges of obtaining reliable performance indicators on snow. However, only a few studies have reported reliability data for ski-specific test protocols. Therefore, this study examined the test-retest reliability of ski-specific aerobic, sprint, and neuromuscular performance tests. Thirty-nine highly trained XC skiers (26 men and 13 women, age: 22 ± 4 years, V̇O2max : 70.1 ± 4.5 and 58.8 ± 4.4 mL·kg-1 ·min-1 , respectively) performed two test trials within 6 days of a diagonal V̇O2max test, n = 27; skating graded exercise test to assess the second lactate threshold (LT2 ), n = 27; 24-min double poling time trial (24-min DP, n = 25), double poling sprint test (SprintDP1 , n = 27), and 1-min self-paced skating sprint test (Sprint1-min , n = 26) using roller skis on a treadmill, and an upper-body strength test (UB-ST, n = 27) to assess peak power (Ppeak ) with light, medium, and heavy loads. For each test, the coefficient of variation (CV), intraclass correlation coefficient (ICC), and minimal detectable change (MDC) were calculated. V̇O2max demonstrated good-to-excellent reliability (CV = 1.4%; ICC = 0.99; MDC = 112 mL·min-1 ), whereas moderate-to-excellent reliability was found for LT2 (CV = 3.1%; ICC = 0.95). Performance during 24-min DP, SprintDP1 , and Sprint1-min showed good-to-excellent reliability (CV = 1.0%-2.3%; ICC = 0.96-0.99). Absolute reliability for UB-ST Ppeak was poor (CV = 4.9%-7.8%), while relative reliability was excellent (ICC = 0.93-0.97) across the loads. In highly trained XC skiers, sport-specific aerobic and sprint performance tests demonstrated high test-retest reliability, while neuromuscular performance for the upper body was less reliable. Using the presented protocols, practitioners can assess within- and between-season changes in relevant performance indicators.

The influence of sub-technique and skiing velocity on air drag in skating style cross-country skiing

In cross-country skiing, velocities range from 2 m s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extrm{s}}^{-1}$$\\end{document} up to more than 20 m s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extrm{s}}^{-1}$$\\end{document} across undulating terrain, and aerodynamics can, therefore, make a large impact on performance. The aim of this study was to investigate the influence of skiing velocity on air drag for skating sub-techniques and downhill postures (tuck). Dynamic and static drag measurements for two athletes were performed in a wind tunnel in relevant velocity ranges for each sub-technique. The drag area decreased with velocity from 2 m s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extrm{s}}^{-1}$$\\end{document} to around 10–12 m s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extrm{s}}^{-1}$$\\end{document}, where it plateaued. No difference in air drag was found between the sub-techniques performed in upright postures (G2–G4) and thereby relatively similar frontal areas. In the G5 sub-technique performed without poling action in a lower posture, the reduced air drag was approximately 28% lower than for G2–G4 at similar velocities, and could even be reduced by an additional 21.7% by keeping the arms tucked in front of the body. In the downhill tucked postures, athletes could reduce air drag by 23% by keeping a low tuck, compared to a high tuck with straight legs. The sub-techniques were tested both dynamically and by averaging the static positions throughout the movements. The air drag was on average 6.1% lower for dynamic movements, indicating that dynamical movements like in cross-country skiing should be tested dynamically when evaluating air drag. Finally, the chosen cycle rate had minimal influence on air drag.